As an increasing number of applications and services are being made available over networks such as the Internet, an increasing number of content, application, and/or service providers are turning to technologies such as cloud computing. Cloud computing, in general, is an approach to providing access to electronic resources through services, such as Web services, where the hardware and/or software used to support those services is dynamically scalable to meet the needs of the services at any given time. A user or customer typically will rent, lease, or otherwise pay for access to resources through the cloud, and thus does not have to purchase and maintain the hardware and/or software needed.
Many cloud computing providers utilize virtualization to allow multiple users to share the underlying hardware and/or software resources. Virtualization can allow computing servers, storage device or other resources to be partitioned into multiple isolated instances (e.g., virtual machines) that are each owned by a particular user. These virtual machines are often hosted using a hypervisor running on a host computing device. In this context, the hypervisor and the guest operating system kernel act as security enforcement mechanisms. For example, the hypervisor typically controls the various virtual machines on the host and the kernel controls the various processes on the virtual machine. For security reasons, both the hypervisor and the kernel are made difficult to modify or alter. Occasionally, however, it may be desirable to modify the code of the hypervisor or the kernel at runtime for reasons, such as to apply software patches, perform security monitoring and the like.